By stashing infrequently-used items in a command bar like this, you can clear up a lot of screen real estate. You don't need to add that extra toolbar or layer of menu items. Keeping the interface clear of options helps reduce the number of things users need to pay attention to at any one time. Which means they're less likely to be overwhelmed and

Avoid providing incorrect affordance cues.

Affordances represent the possibilities in the world for how an agent (a person, animal, or machine) can interact with something. Some affordances are perceivable, others are invisible.

perform less efficiently and be more difficult to use. For example, a door with a handle affords pulling. Sometimes, doors with handles are designed to open only by pushing—the affordance of the handle conflicts with the door’s function. Replace the handle with a flat plate, and it now affords pushing—the affordance of the flat plate corresponds to